A number of different windscreen covers have been tried over time, but none works satisfactorily, and wind noise is still a major disturbance for people who wear hearing aids. Mesh screens have been used, but even if they may dampen wind-noise they have a strong tendency to clog as dirt is inevitably caught and squeezed into the mesh. Also, mesh screens will not keep water out of the microphone opening. Phonak A G has developed a windscreen disclosed in EP 0847227 made of sintered polymer, foamed ceramic, sintered glass or sintered metal. The developed cover is hydrophobic and-or oleo phobic. This prior art cover is with small open pores, whereto a “Teflon®” coating is applied. This cover suffers from the problem that it is not fully sound transparent and also it is rather expensive. None of the prior art techniques seem to provide a microphone cover which both protects the microphone against pollution from the surroundings and diminishes the problems relating to wind-noise in a satisfactory way, while at the same time allows free passage for sound from the surroundings to the microphone element.